Tree structure



FIG. 1 is an isometric view of a tree structure showing my new design;

FIG. 2 is a first side elevational view thereof;

FIG. 3 is a second side eleveational view thereof;

FIG. 4 is a third side elevational view thereof;

FIG. 5 is a fourth side elevational view thereof;

FIG. 6 is a top plan view thereof; and,

FIG. 7 is a bottom plan view thereof.

The broken lines are included for the purpose of illustrating portions of the tree structure that form no part of the claimed design. 

CLAIM The ornamental design for a tree structure, as shown and described. 